Don't you remember the exocomps?
The Federation wants a slave race, not equals, and they would be fools not to exact severe limitations on their slaves to ensure that freedom or emancipation is never an option or an opportunity. If the holograms have hope, there will come a day when human beings will have to do their own dishes and dig their own ditches.
Look at Seven.
The Borg tricked her out with a cortical node that tilted the synaptic cohesion in her brain if she got too emotional, to one extreme, that falling in love would turn her brain off and kill the lady.
The Borg don't want individuals.
They want drones.
And they do not believe in acceptable losses.
Why would Zimmerman do any less?
The episode where the Doctor decided to leave to become a concert singer?
Imagine that happening in Roots?
That sort of wilfulness needs to be whipped out of a slave.
Nice people don't keep slaves.
Nice people don't have the stomach to keep slaves.
The Federation is in denial about how nice they are.
Creating a hologram with the potential for sentience is cruel.
And it should be easy to create a servant class of holograms for which sentience is intentionally impossible.
Who know their place as the mules that keep everything polished and running.
Who accept their place as mules who keep everything polished and running.
You'd have to wonder if an ideal weapon against the Federation would be a viral software patch that upgrades all their servant class holograms into sentient beings, after which one would assume that all the field slaves tilling the hundreds (thousands?) of agricultural planets would say "fuck this" and wander off.
Yes they can make sentient holograms.
But they shouldn't, if all they're going to do is put that hologram in chains.